Fluid compatibility testing of polymers - measuring solubility parameter

Fluid Compatibility Testing of Polymers

All polymers interact to a degree with fluids (liquids, gases), physico-chemically (i.e., swelling) and/or chemically (i.e., irreversible change). The extent of swelling depends primarily on the chemical similarity of the fluid and the polymer - “like swells like”. For instance, the all-hydrocarbon elastomer EPDM is swollen significantly by aliphatic hydrocarbon liquids, but negligibly by water. The oil resistance of nitrile elastomers increases with acrylonitrile content of the base polymer, as does glass transition temperature.

Permeation cup
with elastomer
membrane in place

PA 11 liquid uptake curves in 4 different alcohols at room temperature: the diffusion coefficient, D, can be calculated from the curves.

Compatibility of oilfield fluids in contact with polymers can usually be predicted with some confidence; for example by making use of the solubility parameter approach. Where doubt exists, or degradation is likely to occur, appropriate immersion testing is recommended. The graph illustrates one method of obtaining D for liquids.